Antisense RNA transcribed from "flipped gene" plasmids is an effective method for cell autonomous suppression of exogenous (e.g. viral) as well as endogenous gene activity. We propose to expand our research program on anti-sense RNA to include two additional facets which will encompass RFA #87-CA-18 "Studies of Functional Anti-sense RNA in Oncogenic Viral Systems". Anti-sense gene chimeras will be constructed with URNA, tRNA, and rRNA genes. The level of transcription and the anti-sense inhibition activity of the hybrid genes will be tested in Xenopus oocytes and cultured mammalian cells. The goal of these studies is to exploit both the extremely active promoter signals in these structural RNA genes and, if possible, harness some of the special biological activity of the URNA, tRNA, and rRNA genes to enhance anti-sense RNA activity. Factors that modulate anti-sense RNA activity will be assessed in cultured mammalian cells and in Amphibian embryos. Somatic cell lines with high and low levels of RNA duplex destablizing activity will be selected and the nature of the "unwindase" characterized. Xenopus embryo germ layers and Xenopus tadpole tissues will be tested for unwindase activity that might contribute to tissue- specific gene expression. The capacity of the aforementioned chimeric anti-sense RNAs to overcome the unwindase block will be assessed in each system. Our goal is both to understand and to circumvent this crucial aspect of in vivo RNA-RNA interaction.